The present invention relates generally to the field of excavation and, more particularly, to a system and process for performing subsurface imaging at a site.
Various types of excavators have been developed to excavate a predetermined site or route in accordance with a particular manner of excavation. One particular type of excavator, often referred to as a track trencher, is typically utilized when excavating long continuous trenches for purposes of installing and subsequently burying various types of pipelines and utility conduits. A land developer or contractor may wish to excavate several miles or even hundreds of miles of terrain having varying types of unknown subsurface geology.
Generally, such a contractor will perform a limited survey of a predetermined excavation site in order to assess the nature of the terrain, and the size or length of the terrain to be excavated. One or more core samples may be analyzed along a predetermined excavation route to better assess the type of soil to be excavated. Based on various types of qualitative and quantitative information, a contractor will generally prepare a cost budget that forecasts the financial resources needed to complete the excavation project. A fixed cost bid is often presented by such a contractor when bidding on an excavation contract.
It can be appreciated that insufficient, inaccurate, or misleading survey information can dramatically impact the accuracy of a budget or bid associated with a particular excavation project. An initial survey, for example, may suggest that the subsurface geology for all or most of a predetermined excavation route consists mostly of sand or loose gravel. The contractor""s budget and bid will, accordingly, reflect the costs associated with excavating relatively soft subsurface soil. During excavation, however, it may instead be determined that a significant portion of the predetermined excavation route consists of relatively hard soil, such a granite, for example. The additional costs associated with excavating the undetected hard soil are typically borne by the contractor. It is generally appreciated in the excavation industry that such unforeseen costs can compromise the financial viability of a contractor""s business.
The present invention is directed to systems and methods for performing subsurface imaging. According to one embodiment, a system of the present invention includes a portable structure and a subsurface imaging system supported by the portable structure. In one configuration, the subsurface imaging system includes a plurality of antennae. At least a first antenna of the plurality of antennae is oriented in a manner differing from an orientation of a second antenna of the plurality of antennae. By way of example, the first antenna is orientated substantially orthogonal to the second antenna. The plurality of antennae may, for example, operate in a bi-static mode.
The system further includes transmitter circuitry, coupled to the plurality of antennae, for generating electromagnetic probe signals. Receiver circuitry, coupled to the plurality of antennae, receives electromagnetic return signals resulting from transmission of the electromagnetic probe signals. A processor is provided for processing the received electromagnetic return signals. A display may be provided as part of the subsurface imaging system and/or as part of a processing system separate from the subsurface imaging system which processes the received electromagnetic return signals. The processor can generate two-dimensional and/or three-dimensional detection data using the received electromagnetic return signals. The processor, for example, can generate data representative of a volume of the subsurface within which a detected subsurface object or feature is located. One or more geophysical instruments can also be supported on the portable structure for sensing one or more geophysical characteristics of the subsurface subjected to imaging.
According to another embodiment, a subsurface imaging system supported by a portable structure includes transmitter circuitry for generating electromagnetic probe signals and a plurality of transmit antennae coupled to the transmitter circuitry. A plurality of receive antennae is provided for receiving electromagnetic return signals, and receiver circuitry is coupled to the receive antennae. The plurality of antennae, by way of example, can operate in a bi-static mode. By way of further example, at least two of the transmit antennae can be oriented substantially orthogonal to one another, and at least two of the receive antennae can be oriented substantially orthogonal to one another.
According to this embodiment, a positioning system detects a position of the portable structure. The positioning system, for example, can be a range radar positioning system, an ultra-sonic positioning system, or a global positioning system (GPS).
A processor processes received electromagnetic return signals. The processor also associates position data acquired by the positioning system with return signal data to generate location data representative of a location of an underground object subjected to the electromagnetic probe signals. For example, the processor, using the received electromagnetic return signals and position data acquired by the positioning system, can generate a map of a subsurface over which the portable structure is moved.
In accordance with a further embodiment, a method of imaging a subsurface involves transmitting, while moving a plurality of antennae, electromagnetic probe signals into the subsurface. While moving the plurality of antennae, electromagnetic return signals are received from the subsurface. Positioning data associated with movement of the plurality of antennae is generated. One or more geophysical parameters associated with the subsurface can also be acquired. The return signals and positioning data are processed to generate location data representative of a location of an underground object or feature within the subsurface. Such information can be produced and displayed in a two-dimensional and/or three-dimensional form. For example, the return signals and positioning data can be used to generate a map of a subsurface over which the portable structure is moved.
Various methods have been developed to analyze subsurface geology in order to ascertain the type, nature, and structural attributes of the underlying terrain. Ground penetrating radar and infrared thermography are examples of two popular methods for detecting variations in subsurface geology. These and other non-destructive imaging analysis tools, however, suffer from a number of deficiencies that currently limit their usefulness when excavating long, continuous trenches, or when excavating relatively large sites. Further, conventional subsurface analysis tools typically only provide an image of the geology of a particular subsurface, and do not provide information regarding the structural or mechanical attributes of the underlying terrain which is critical when attempting to determine the characteristics of the soil to be excavated.
There is a need among developers and contractors who utilize excavation machinery to minimize the difficulty of determining the characteristics of subsurface geology at a predetermined excavation site. There exists a further need to increase the production efficiency of an excavator by accurately characterizing such subsurface geology. The present invention fulfills these and other needs.